1. Field of the Invention
The present invention relates to a method and a device for testing for the occurrence of bit errors, and in particular to a method and a device for conducting a test for the occurrence of bit errors in a plurality of communication devices.
2. Description of the Related Art
As a method and a device for efficiently testing a plurality of communication devices, following prior art technologies have been already proposed.
Prior Art (1) (See FIG. 6)
As many signal generators 1-1-1-n and bit error measuring devices 5-1-5-n as n (≧2) units of measured devices 3-1-3-n are provided to configure respective measurement systems in parallel. Testing signals generated at the signal generators 1-1-1-n are respectively provided to the measured devices 3-1-3-n, and the output signals therefrom are respectively transmitted to the bit error measuring devices 5-1-5-n to measure bit errors (bit error rate). Thus obtained bit errors in each measurement system are transmitted to a common measurement controller 10, which commonly controls the signal generators 1-1-1-n, whereby the measured devices 3-1-3-n are tested in parallel.
Prior Art (2) (See FIG. 7)
Only a common single signal generator 1 is connected to n units of measured devices 3-1-3-n. The common testing signal from this signal generator 1 is provided to the measured devices 3-1-3-n, the output signals therefrom are measured at the bit error measuring devices 5-1-5-n, and the signal generator 1 is controlled through the measurement controller 10 in the same way as the above-mentioned prior art (1), whereby the measured devices 3-1-3-n are tested in parallel.
Prior Art (3) (See FIG. 8)
A single signal generator 1 in the case of the above-mentioned prior art (2) and a single bit error measuring device 5 are provided to measured devices 3-1-3-n, which are connected in tandem. The testing signal from the signal generator 1 is provided to the measured device 3-1, and the output signal therefrom is provided to the bit error measuring device 5 sequentially through the measured devices 3-2-3-n. 
However, the above-mentioned prior art (1) is not different from the technology of simply providing a plurality of measurement systems respectively composed of a single signal generator, a single measured device, and a single bit error measuring device, so that a measurement operation without operator's intervention is only achieved by automatically controlling these plural measurement systems with the common measurement controller 10. For this reason, expensive measuring devices like signal generators and bit error measuring devices have to be prepared in number as many as the measured devices for which a parallel measurement is desired to be performed, which leads to enlargement of a measurement scale and increase in cost.
Also, it is impossible to simultaneously control each of the measured devices, in which setting and data collection have to be performed sequentially, whereby a measurement speed is lowered as a whole.
Also, in the above-mentioned prior art (2), only a single signal generator is required. However, since the output of the signal generator is commonly transmitted to the measured devices 3-1-3-n, n units of bit error measuring devices are still required so that the number of bit error measuring devices can not be reduced.
Furthermore, in the above-mentioned prior art (3), only a single signal generator and a single bit error measuring device are required. However, when a bit error occurs on the way from the measured device 3-1 to the measured device 3-n, the output signal of the concerned measured device in which the bit error has occurred becomes a signal including the bit error. Therefore, the measured devices connected following the concerned device can no longer be tested. As a result, the only thing that can be determined is whether or not a bit error exists on all of the measured devices as a whole.